1. Field of the Invention
This invention relates to the transmission of an electric signal by electric conduction between a driving wheel and a vehicle.
2. Brief Description of the Related Art
Monitoring the inflation pressure of tires poses a problem so far poorly solved; that of the transmission of information between a rotating element, namely the wheel, and the vehicle to which this wheel is connected. More precisely, the problem to be solved is that of transferring information from "the stationary portion of the vehicle" to the mobile elements in rotation relative to this stationary portion. The stationary portion particularly comprises the suspension arms and the wheel carrier which, although not entirely stationary, do not rotate.
Devices using electric conduction to transmit an electric signal require the presence of a rotating electric contact in at least one point in the electric circuit. To avoid resorting to a device with rings and brushes of the type used in electric motors, U.S. Pat. No. 2,235,930 proposes placing a rotating electric contact on the axis of rotation of the wheel, at the end of the hub.
U.S. Pat. No. 4,489,599 uses a bearing instead of a rotating electric contact to provide the transmission of an electric signal. However, the device there proposed is complex to fabricate, particularly because it requires making two mechanically complex electric connections, that is to say one connection per bearing race. Further, there must be at least two wheel bearings, in order for the second bearing to provide grounding to the vehicle in the standard way, as is the case for circuits that monitor the wear of brake linings. Recent developments in automobile mechanics have led to wheel supports providing only one bearing per wheel, i.e., a bearing using a single stationary race and a single rotating race. The trend to parts integration has even lead to designing bearings, one of whose races itself constitutes the hub or wheel carrier. These developments are not compatible with the solution proposed by U.S. Pat. No. 4,489,599.